Device and a method for aligning sheets

ABSTRACT

Sheets which are overlapped with an offset are supplied to a device for the continuous alignment of sheets by a stream feeder. After alignment of at least the front edge and one lateral edge of each sheet, the sheets can be transferred downstream to a following device.

[0001] The invention relates to a device and a method for aligning sheets in accordance with the preambles of claims 1 or 6.

[0002] A device and a method for aligning sheets is known from EP 0 120 348 A2. There, the alignment of the front edges of the sheets takes place in a way wherein the sheets, arranged in the manner of fish scales, are fed to the device and are fed to an alignment cylinder of the device at a conveying speed which is at least greater than the circumferential speed of the alignment cylinder. Front lays are arranged on the circumference of the alignment cylinder, against which the front edges of the sheets can be placed. Because of the relative speeds of the sheets and the front lays, the front edge of the sheets is braked at least slightly, and the front edge of the sheet is aligned by means of this. Following the alignment of the front edge of the sheet, the area of the front edge of the sheet is fixed on a suction strip by means of the application of a vacuum, so that the sheets is looped around the circumference of the alignment cylinder because of the continued rotatory driving of the alignment cylinder. Following the alignment of the front edge of the sheet and prior to transferring the sheet to a downstream-located device, the lateral offset of a lateral edge of the sheet is measured by means of a measuring device. The suction strip on which the front edge of the sheet is fixed is linearly displaced axially in the direction of the axis of rotation of the alignment cylinder as a function of the result of the measurement in order to align the lateral edge of the sheet in accordance with the desired alignment. The result of this is that the sheet can be transferred, placed in the correct position in regard to its front edge, as well as to a lateral edge, to a subsequent device, for example a sheet-printing press.

[0003] A device for sheet guidance of a sheet-fed rotary printing press is known from DE 23 13 150 C3, wherein the sheets are conducted on a feed table in scaled layers to the device and then away from the device. The use of suction rollers, on whose entire circumferences recesses are provided, for conveying the sheets lying flat on the feed table is described. The sheet can be fixed on the circumference of the suction roller by applying a vacuum. In this case the suction roller is arranged in a recess of the feed table in such a way that the sheets, which lie flat on the feed table and tangentially against the circumference of the suction roller, can be driven. It is achieved by means of this that the respective sheets come into contact with the suction roller only in a line-shaped contact area, wherein the driving forces are frictionally transmitted by the suction roller to the sheet in the line-shaped contact area. Thus no looping of the sheets around the suction rollers is required.

[0004] A device with a suction drum is known from WO 97/35795 A1, to whose circumference the sheets to be conveyed can be frictionally fixed by means of the application of a vacuum. In this case the drive mechanism of the suction drum is designed in such a way that the number of revolutions and/or the angle of rotation of the suction drum can be controlled by an independent electrical motor in accordance with pre-selected movement laws.

[0005] A sheet-feeding device for printing presses is known from DE-AS 20 46 602, in which the lateral offset of a lateral edge of a sheet in relation to a desired orientation can be detected by means of a measuring device. For aligning the lateral edge of the sheet it is possible to displace an alignment cylinder, on whose circumference the sheet is fixed, axially in the direction of its axis of rotation as a function of the measurement result.

[0006] A contactless operating device for measuring the position of sheets is known from EP 0 716 287 A2, wherein the lateral edges of the sheets can be measured by means of an optical system.

[0007] DE 42 39 732 A1 shows a device for aligning sheets, wherein the sheets are initially pre-aligned by means of a belt system, and are thereafter finely aligned by means of a suction roller.

[0008] U.S. Pat. No. 5,078,384 discloses a device for aligning sheets by means of two individually driven wheels, which are controlled by a first sensor signalling the arrival of the sheets, and two sensors detecting the oblique position of the sheet.

[0009] The object of the invention is based on creating a device and a method for the alignment of sheets.

[0010] In accordance with the invention, this object is attained by the characteristics of claims 1 or 6.

[0011] The advantages to be obtained by means of the invention consist in particular in that the edge offset of the sheet can be measured by a total of four sensors prior to, during and subsequent to the alignment, wherein the results of the measurements of the different sensors can be used, on the one hand, for controlling the various actuators, in particular the alignment cylinder, by means of which the alignment of the sheets can be affected, and a substantially continuous control and/or documentation of the sheet alignment is assured at the same time. By means of measuring the sheet alignment during the various phases of the conveyance in particular, a pre-alignment of the sheets prior to the actual fine alignment at the alignment cylinder becomes possible. Moreover, a final check of the sheet alignment becomes possible prior to their transfer to downstream-connected devices, for example a transfer cylinder, so that in case the permissible position tolerances are exceeded, for example, no transfer takes place, and the respective sheet is removed.

[0012] If a fifth sensor is provided in addition in the device, which is arranged downstream in the conveying direction from the third sensor, the edge offset of the front edge of the sheet can still be measured and controlled in the course of the alignment of the sheet by the alignment cylinder, so that the alignment can still be corrected as a function of the result of the measurement by the fifth sensor by an appropriate actuation movement of the alignment cylinder.

[0013] A further advantage of the invention lies in that a novel way of functioning of the actuator for aligning the edges of the sheet is proposed. Different than with the known alignment cylinders, on whose circumferences front lays are provided, so that an alignment of the sheet is achieved by means of the relative speed difference between the front lays and the sheet edge, in accordance with the teaching of the present invention the sheet can be aligned because at least two cylinder elements are provided at the alignment cylinder, each of which can come into contact with the sheet and which can be adjusted relative to each other in respect to the axis of rotation of the alignment cylinder. In other words, this means that during their contact with the sheet, the cylinder elements move at different absolute speeds, wherein this speed difference is transmitted to the sheet by the contact between the cylinder elements and the sheets. Because of the speed difference, the various sections of the sheets are conveyed over different distances while they rest against the alignment cylinder, so that it is possible to achieve a directed alignment movement of the sheet by an appropriate selection of the relative speed between the cylinder elements.

[0014] How the relative speed between the cylinder elements of the alignment cylinder is realized is basically unimportant. For example, it would be conceivable for the cylinder elements to rotate together on a base body at a defined basic speed, and that for aligning the sheet the cylinder elements can each be displaced in relation to the base body, and therefore relative to the respectively other cylinder element. It is also conceivable for the cylinder elements to each be driven independently of each other, wherein it is necessary in this case for the cylinder elements to be driven synchronously, i.e. at the same drive speed, for conveying the sheets without aligning the edges.

[0015] Exemplary embodiments of the invention are represented in the drawings and will be described in greater detail in what follows.

[0016] Shown are in:

[0017]FIG. 1, in a schematically represented cross section, a first exemplary embodiment of a device for the continuous alignment of sheets,

[0018]FIG. 2, the device in FIG. 1 in a schematically represented lateral view,

[0019]FIG. 3, in a schematically represented cross section, a second exemplary embodiment of a device for the continuous alignment of sheets,

[0020]FIG. 4, the device in FIG. 3 in a schematically represented lateral view.

[0021] A first exemplary embodiment of a device 01 for the continuous alignment of sheets, in particular for feeding sheets to a web-fed rotary printing press, is represented in FIGS. 1 and 2. A first frame element 03 with three linear guides 04 is seated, axially displaceable, on a second frame element 02 embodied in the manner of a rack. An alignment device 06, for example an alignment cylinder 06 which substantially consists of a drive shaft 07 and two suction rollers 08, 09, which are arranged spaced apart from each other on the drive shaft 07, is rotatably seated in the first frame element 03.

[0022] A drive motor 11, which is fixed to the frame of the second frame element 02 and whose drive movement is transmitted to the drive shaft 07 via a coupling 12 which makes a linear adjustment possible, is used for the rotatory driving of the alignment cylinder 06.

[0023] A front lay 13 is fastened on the circumference of each of the suction rollers 08, 09. A sheet 14 being fed together with other sheets to the device 01 from a fanning device, not represented, comes into contact at a relative speed with the front lays 13, so that the front edge of the sheet 14 is aligned at the front lays 13 by being braked. Following the alignment of the front edge of the sheet 14, the sheet 14 is fixed on the suction rollers 08, 09 by the application of an underpressure, for example of 0.2 to 0.6 bar, from a vacuum source in suction chambers, not represented. In this case the sheet 14 rests flat on a feed table 16 arranged on the top of the first frame element 03, and is non-positively connected with the first frame element 03 via the suction rollers 08, 09.

[0024] While the suction rollers 08, 09 continue to rotate and thereby convey the sheet 14 on in the conveying direction, the entire first frame element 03, together with the alignment cylinder 06 and the feed table 16, can be axially displaced in the direction of the axis of rotation of the alignment cylinder 06 for aligning a lateral edge of the sheet 14. A drive motor 17 is used for this which, via a coupling 18, drives a ball screw spindle 21 seated in a fixed bearing 19. A threaded nut 22 is fastened in the lateral component wall of the first frame element 03 and is in engagement with the ball screw spindle 21, so that the entire first frame element 03 can be displaced in the linear guides 04 by driving the ball screw spindle 21.

[0025] Two hubs 37, 38, which are connected, fixed against relative rotation, with the drive shaft 07, are provided for transmitting torque from the drive shaft 07 to the suction rollers 08, 09, and can be displaceably fixed on the drive shaft 07 for changing formats. The suction drums 08, 09 can be turned on the hubs 37, 38 for the circumferential adjustment of the front lays 13, wherein fine adjustment devices 39 are provided between the hubs 37, 38 on the one hand, and the suction rollers 08, 09 on the other, for the fine adjustment of the front lays 13.

[0026] The device 01 with the drive motors 11, 17, the suction roller 08 and the front lay 13 arranged on it, the feed table 16 constituted from three plates 23, 24, 26, the linear guides 04 and the first frame element 03 are schematically represented in a lateral view in FIG. 2. A total of four sensors 27, 28, 29, 31 is provided for measuring the edge offset of the sheets 14 to be aligned in the device 01. The edge offset, in particular the edge offset of the front edge of a sheet 14, can be measured by the sensor 27 prior to entry into the device 01. An actuator 32, constituted by two conveyor belts extending parallel in respect to each other, is positioned ahead of the device 01 for pre-aligning the sheets 14 prior to the actual alignment in the device 01. The conveyor belts 33, 34, which are shown located one behind the other in FIG. 2, can be driven at different speeds as a function of the measurement result from the sensor 27, so that an alignment movement of the sheets 14 around a vertical axis is generated by means of the differential speed. In principle it is arbitrary whether a front edge or a lateral edge of the sheets 14 is aligned by means of the actuator 32, this is a question of the respective intended application. However, in most cases a front edge of the sheets 14 will be pre-aligned by means of the actuator 32.

[0027] Following the pre-alignment by means of the actuator 32, the sheets 14 are conveyed into the device 01, and their front edges come to rest against the front lays 13, which rotate at least slightly slower. Because of the relative speed difference between the sheets 14 and the front lays 13, the front edge runs up on the front lays 13 and is aligned in the process. As soon as the front lays 13 have passed the highest point during the rotation, the alignment of the front edge of a sheet 14 is essentially finished and is checked by means of a measurement by the sensor 29.

[0028] By means of continued driving of the suction rollers 08, 09, the sheet 14 is conveyed on in the device 01 and, following the alignment of the front edge at the front lays 13, the edge offset of a lateral edge of the sheet 14 is surveyed by means of the sensor 28. As a function of this measured result, the first frame element 03 is linearly displaced by driving the drive motor 17 until the difference between the desired alignment of the lateral edge and the measured actual alignment has reached zero. The sheet 14 is conveyed on in the conveying direction by means of the continued driving of the suction rollers 08, 09 also during the alignment of the lateral edge of the sheet 14. In the course of this the suction rollers 08, 09 are accelerated by the drive motor 11 in such a way that upon reaching one of the devices 36 located downstream of the device 01, for example a transfer cylinder 36, the sheet 14 has the same speed as the downstream-located device 36. During the transfer of the sheet 14 from the device 01 to the downstream-located device 36, the alignment of the front edge of the sheet 14 is again surveyed by means of the sensor 31 in order to check that preset positional tolerances have been maintained.

[0029] A further exemplary embodiment of a device 41 is represented in FIGS. 3 and 4, whose structure essentially corresponds to the structure of the device 01 of FIG. 1, consisting of a second frame element 02, first frame element 03, linear guides 04, feed table 16 and the transverse displacement arrangement constituted by the drive motor 17, the coupling 18, the fixed bearing 19, the threaded spindle 21 and the threaded nut 22.

[0030] The alignment cylinder 06 of the device 41 has two independent drive trains, which can drive the sheets 14 independently of each other. Different from the device 01, with the device 41 the alignment cylinder 06 is not driven by a drive shaft 07, but by two drive shafts 42, 43, so that the circumferential speeds of elements 44, 46, for example cylinder elements 44, 46, in particular suction rollers 44, 46, can be set independently from each other by an appropriate actuation of two drive motors 47, 48.

[0031] For the normal conveyance of the sheets 14 in the conveying direction, the drive motors 47, 48 are actuated synchronously with each other, so that the cylinder elements 44, 46 rotate at the same circumferential speed. No front lays as in the device 01 are provided on the cylinder elements 44, 46 for aligning an edge of the sheet 14, in particular for aligning the front edge. Instead, for aligning the sheet 14, the drive motors 47, 48 are actuated by the control in such a way, that the cylinder elements 44, 46 have a defined speed difference, by means of which a rotatory movement around a vertical ordinate axis is superimposed on the linear conveying movement of the sheets 14 in the conveying direction. A corresponding edge of the sheet 14 can be aligned by means of the rotatory movement around the vertical ordinate axis.

[0032] For making possible the required linear compensation between the drive motors 47, 48, on the one hand, and the drive shafts 42, 43, on the other hand, which is required for aligning the lateral edge of the sheet 14, appropriately designed couplings 12, which permit a linear compensation, are again used.

[0033]FIG. 4 shows the device 41 with the upstream-located actuator 32 and the downstream-located device 36 in a schematically represented lateral view. The functioning of the sensors 27, 28, 31 for actuating the actuator 32, or of the transverse displacement device, or for the final check of the sheet alignment, corresponds to the functioning of the device 01 (see FIG. 2). But different from the device 01, with the device 41 two sensors 49, 51 are arranged one behind the other in the conveying direction of the sheets 14 above the cylinder elements 44, 46. The edge offset of the front edge of a sheet 14 is measured by the sensor 49 immediately prior to the transfer of the sheet 14 to the cylinder elements 44, 46, and thereafter the relative speed between the cylinder elements 44, 46 is selected as a function of the measured result from the sensor 49 in such a way, that the desired alignment of the front edge is achieved. The alignment of the front edge of the sheet 14 subsequently to the first alignment movement is controlled by the sensor 51 by means of the appropriate relative speed between the cylinder elements 44, 46, wherein the sheets 14 still rest against the cylinder elements 44, 46 at the time of the check by the sensor 51. If the measurement by the sensor 51 shows a deviation of the alignment of the front edge which cannot be tolerated, the cylinder elements 44, 46 are again driven at appropriate relative speeds in order to correct the alignment of the front edge.

[0034] Only after correction of the alignment of the front edge is the alignment of the lateral edges measured by means of the sensor 28 and they are aligned by driving the motor 17.

[0035] List of Reference Numerals

[0036]01 Device

[0037]02 Frame element, second

[0038]03 Frame element, first

[0039]04 Linear guide

[0040]05 -

[0041]06 Alignment device, alignment cylinder

[0042]07 Drive shaft

[0043]08 Suction roller

[0044]09 Suction roller

[0045]10 -

[0046]11 Drive motor

[0047]12 Coupling

[0048]13 Front lay

[0049]14 Sheet

[0050]15 -

[0051]16 Feed table

[0052]17 Drive motor

[0053]18 Coupling

[0054]19 Fixed bearing

[0055]20 -

[0056]21 Ball screw spindle

[0057]22 Threaded nut

[0058]23 Plate (16)

[0059]24 Plate (16)

[0060]25 -

[0061]26 Plate (16)

[0062]27 Sensor

[0063]28 Sensor

[0064]29 Sensor

[0065]30 -

[0066]31 Sensor

[0067]32 Actuator

[0068]33 Conveyor belt

[0069]34 Conveyor belt

[0070]35 -

[0071]36 Device, transfer cylinder, downstream-located

[0072]37 Hub

[0073]38 Hub

[0074]39 Fine adjustment device

[0075]40 -

[0076]41 Device

[0077]42 Drive shaft

[0078]43 Drive shaft

[0079]44 Element, cylinder element, suction roller

[0080]45 -

[0081]46 Element, cylinder element, suction roller

[0082]47 Drive motor

[0083]48 Drive motor

[0084]49 Sensor

[0085]50 -

[0086]51 Sensor 

1. A device for the alignment of a sheet (14), having sensors (27, 28, 29, 31, 49, 51) which measure the position of the sheet (14), characterized in that at least three sensors (27, 28, 29, 31, 49, 51) measuring the respective position of the sheet, are arranged one behind the other in respect to the conveying direction of the sheet (14).
 2. The device in accordance with claim 1, characterized in that an actuator (32) for aligning a sheet (14) as a function of the result of the measurement by a sensor (27) is arranged upstream of the alignment cylinder (06), characterized in that the first sensor (27) is arranged upstream of the actuator (32), a second sensor (29, 49) between the actuator (32) and the alignment cylinder (06), and a third sensor (31) downstream of the alignment cylinder (06), each in respect to the conveying direction of the sheets (14), for measuring the edge offset of the front edge of the sheet (14).
 3. The device in accordance with claim 1, characterized in that the third sensor (31) is arranged for measuring the edge offset of the front edge of the sheet (14) directly prior to or during the transfer of the sheet (14) to a downstream-arranged device (36).
 4. The device in accordance with claim 1, characterized in that a fourth sensor (51) is provided for measuring the edge offset of the front edge of the sheet (14) during the adherence of the sheet (14) to an alignment cylinder (06) and is arranged downstream of the second sensor (49) in the conveying direction of the sheets (14).
 5. The device in accordance with claim 1, characterized in that a further sensor (28) is arranged for measuring an edge offset of a lateral edge of the sheet (14), and that a further sensor (27) is arranged for measuring an edge offset of a front edge of a sheet (14) prior to or during the entry of the sheet (14) into the device (01, 41).
 6. A method for the alignment of a sheet (14), having sensors (27, 28, 29, 31, 49, 51) which measure the position of the sheet (14), characterized in that measurements of the position of the sheet (14) are taken in at least three locations arranged one behind the other in respect to the conveying direction of the sheet (14).
 7. The method in accordance with claim 6, characterized in that the edge offset of the sheet (14) is measured at each of these three locations.
 8. The method in accordance with claim 6, characterized in that the edge offset of the front edge is measured by means of one sensor (29, 49) immediately before, or during, or directly after the transfer of a sheet (14) to an alignment cylinder (06), and the front edge of the sheet (14) is aligned as a function of the measurement result of this sensor (29, 49) by means of the alignment cylinder (06), wherein the edge offset of a lateral edge of the sheet (14) in the device (01, 41) is measured with a second sensor (28), and the lateral edge of the sheet (14) is aligned by means of a transverse displacement device (17, 18, 19, 21, 22) as a function of the measurement result of the second sensor (28), wherein the edge offset of a front edge of the sheet (14) is measured by a further sensor (27) prior to or during the entry of the sheet (14) into the device (01, 41), and the sheet is pre-aligned as a function of the measurement result of the sensor (27) by means of an actuator (32) placed upstream of the alignment cylinder (06).
 9. The method in accordance with claim 6, characterized in that the edge offset of the front edge of the sheet (14) is measured by a fourth sensor (31) directly prior to or during the transfer of the sheet (14) to a downstream-arranged device (36).
 10. The method in accordance with claim 9, characterized in that the edge offset of the front edge of the sheet (14) is measured by a fifth sensor (51), which is arranged downstream of the third sensor (49) in the conveying direction of the sheets (14), while the sheet (14) adheres to the alignment cylinder (06), wherein subsequently the alignment of the front edge of the sheet (14) is corrected as a function of the result of the measurement by the fifth sensor (51) by means of actuating the alignment cylinder (06). 